Field of the Invention
The present invention relates to a development device detachably mounted to an image forming apparatus.
Description of the Related Art
An electrophotography image forming apparatus (hereinbelow referred to as an “image forming apparatus”) such as a copy machine, a facsimile, and a printer using an electrophotography process uniformly charges a photosensitive drum to form a latent image (electrostatic latent image) by selective exposure onto the photosensitive drum. The latent image is developed with toner (developer), actualized (visualized) as a toner image, and then transferred onto a recording medium. Heat and pressure are applied to the transferred toner image to fix the toner image onto the recording medium. Thus, an image is recorded on a recording member.
Since such an image forming apparatus requires tonner supply or maintenance of various types of process units, an image forming apparatus adopting a process cartridge method is known, as a unit for facilitating a tonner supply operation or maintenance. All or part of the photosensitive drum, a charging unit, a development unit, and a cleaning unit are put together in a frame member to be contained in a cartridge, which is detachably mounted to the main body of the image forming apparatus. By the process cartridge method, a user can perform the maintenance of the apparatus by replacing a development device or a process cartridge, thereby significantly improving operability. Thus, the process cartridge method has been widely used for the image forming apparatus.
The process cartridge method includes various types according to configurations for integrally forming units as a cartridge. For example, there is provided a development cartridge in which a developing roller for developing an electrostatic latent image formed on a photosensitive drum, a development frame member for storing toner, and a developing blade are disposed. There is also provided the process cartridge in which the photosensitive drum is further added to the development cartridge.
To prevent leakage of toner from the development frame member for storing the toner, various types of sealing members are provided at various portions of a development device in the development cartridge and the process cartridge. First, as a first sealing member, a flexible sheet member is provided on the development frame member. The flexible sheet member abuts on the surface of the developing roller entirely in a longitudinal direction of the rotating developing roller (the axis direction of the developing roller) to prevent the toner from leaking from between the development frame member and the developing roller. Further, as a second sealing member, a bottom sealing member is provided entirely in the longitudinal direction of the developing roller. The bottom sealing member prevents the toner from leaking from between the developing blade and the development frame member. Furthermore, as a third sealing member, a development edge portion sealing member is provided near both ends of the developing roller in the longitudinal direction. The development edge portion sealing member prevents the toner from leaking from between the development frame member and the developing roller.
As a sealing unit for preventing the toner from leaking from a portion surrounded by the development edge portion sealing member, the development frame member, and the flexible sheet member, Japanese Patent Application Laid-Open No. 2000-105501 discusses the sealing unit having a sealing configuration in which an elastic sealing member is disposed to closely contact the above-described portions.
The longer operating life of the development device can generate continuous shock caused by increase in the number of repetitions of separation and abutment between the developing roller and the photosensitive drum for an image forming operation. The longer operating life of the development device can also generate a friction force acting for longer hours between the developing roller and the development edge portion sealing member caused by driving of the developing roller. In the above-described sealing configuration of the conventional example, this friction force acts in a direction in which the development edge portion sealing member and the elastic sealing member are separated from each other. If the operating life of the development device is extended, it may be difficult to maintain adhesion between the development edge portion sealing member and the elastic sealing member.
To solve the above-described problem, the development edge portion sealing member using material having better airflow is adopted, the elastic sealing member in a fluid state, which is melted at a high temperature when assembled, is infiltrated into the material having higher air permeability, to improve close contact between the development edge portion sealing member and the elastic sealing member.
However, the longer operating life of the development device can generate the continuous shock caused by the increase in the number of repetitions of separation and abutment between the developing roller and the photosensitive drum, and the toner may infiltrate into the development edge portion sealing member using the material having higher air permeability. This may cause toner leakage.